mybatis入门
官网https://mybatis.org/mybatis-3/zh_CN/getting-started.html
1. 入门案例
1.1 创建user表，添加数据
create database mybatis;
use mybatis;
alter database mybatis charset utf8mb4;
# 注意：不设置可能会出现报错 “ Incorrect string value: ‘\xE7\x94\xB7‘ for column ‘xx‘ at row x”
drop table if exists tb_user;
create table tb_user(
id int primary key auto_increment,
username varchar(20),
password varchar(20),
gender char(1),
addr varchar(30)
);
INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京');
INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津');
INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');
select * from tb_user;
1.2 创建模块，导入坐标
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.example</groupId>
<artifactId>mybatis-demo</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.5</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.20</version>
</dependency>
<!-- 添加logback-classic依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
<!-- 添加logback-core依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.2.3</version>
</dependency>
</dependencies>
</project>
1.3 编写mybatis核心配置文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<environments default="development">
<environment id="development">
<transactionManager type="JDBC"/>
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="root"/>
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="userMapper.xml"/>
</mappers>
</configuration>
1.4 编写sql映射文件
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="test">
<select id="selectAll" resultType="com.itheima.pojo.User">
select * from tb_user
</select>
</mapper>
1.5 编码
package com.itheima.pojo;
public class User {
private Integer id;
private String username;
private String password;
private String gender;
private String addr;
// get set 方法
}
package com.itheima;
import com.itheima.pojo.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import java.io.InputStream;
import java.util.List;
public class MybatisDemo {
public static void main(String[] args) throws Exception {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
List<User> users = sqlSession.selectList("test.selectAll");
System.out.println(users);
users.forEach(System.out::println);
sqlSession.close();
}
}
2. Mapper代理开发
2.1 步骤1
注意：创建resources的目录，通过com/itheima/mapper创建多级目录
2.2 步骤2
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.UserMapper"> # namespace为接口的全限定类名
<select id="selectAll" resultType="com.itheima.pojo.User">
select * from tb_user
</select>
</mapper>
2.3 步骤3
<mappers>
<!-- <mapper resource="com/itheima/mapper/userMapper.xml"/>-->
<package name="com.itheima.mapper"/> 统一扫描多个mapper.xml配置文件
</mappers
2.4 步骤4
// List<User> users = sqlSession.selectList("test.selectAll");
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> users = userMapper.selectAll();
3. 核心配置文件
3.1 typeAliases
4. 案例
4.1 准备工作
4.1 数据表
-- 删除tb_brand表
drop table if exists tb_brand;
-- 创建tb_brand表
create table tb_brand
(
-- id 主键
id int primary key auto_increment,
-- 品牌名称
brand_name varchar(20),
-- 企业名称
company_name varchar(20),
-- 排序字段
ordered int,
-- 描述信息
description varchar(100),
-- 状态：0：禁用 1：启用
status int
);
-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织，构建万物互联的智能世界', 1),
('小米', '小米科技有限公司', 50, 'are you ok', 1);
SELECT * FROM tb_brand;
4.2 实体类
public class Brand {
// id 主键
private Integer id;
// 品牌名称
private String brandName;
// 企业名称
private String companyName;
// 排序字段
private Integer ordered;
// 描述信息
private String description;
// 状态：0：禁用 1：启用
private Integer status;
// get set 方法
}
4.3 测试用例
4.4 mybatisX插件
4.2 查询所有数据
import com.itheima.pojo.Brand;
import java.util.List;
public interface BrandMapper {
List<Brand> selectAll();
}
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.BrandMapper">
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName" />
<result column="company_name" property="companyName" />
</resultMap>
<select id="selectAll" resultMap="brandResultMap">
select *
from tb_brand;
</select>
</mapper>
package com.itheima.pojo;
import lombok.Data;
@Data
public class Brand {
// id 主键
private Integer id;
// 品牌名称
private String brandName;
// 企业名称
private String companyName;
// 排序字段
private Integer ordered;
// 描述信息
private String description;
// 状态：0：禁用 1：启用
private Integer status;
}
package com.itheima.test;
import com.itheima.mapper.BrandMapper;
import com.itheima.pojo.Brand;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
public class MybatisTest {
@Test
public void testSelectAll() throws IOException {
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
List<Brand> brands = brandMapper.selectAll();
brands.forEach(System.out::println);
sqlSession.close();
}
}
4.3 查询某条数据
public interface BrandMapper {
Brand selectById(int id);
}
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.itheima.mapper.BrandMapper">
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName"/>
<result column="company_name" property="companyName"/>
</resultMap>
# parameterType="int" 可以省略
<select id="selectById" parameterType="int" resultMap="brandResultMap">
select * from tb_brand where id = #{id};
</select>
</mapper>
@Test
public void testSelectById() throws IOException {
int id = 2;
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
Brand brand = brandMapper.selectById(id);
System.out.println(brand);
sqlSession.close();
}
4.4 条件查询
注意：数据库连接建议设置成utf-8编码，否则查询中文时容易查不出结果
<property name="url" value="jdbc:mysql:///mybatis?characterEncoding=UTF-8&useSSL=false"/>
public interface BrandMapper {
List<Brand> selectByCondition(@Param("status") int status, @Param("companyName") String companyName);
}
<select id="selectByCondition" resultMap="brandResultMap">
select * from tb_brand
<where>
<if test="status != null">
and status = #{status}
</if>
<if test="companyName != null ">
and company_name like #{companyName}
</if>
<if test="brandName != null and brandName != '' ">
and brand_name like #{brandName}
</if>
</where>
</select>
public void testSelectByCondition() throws IOException {
int status = 1;
String companyName = "华为";
String brandName = "华为";
companyName = "%" + companyName + "%";
brandName = "%" + brandName + "%";
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession();
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
List<Brand> brands = brandMapper.selectByCondition(status, companyName, brandName);
brands.forEach(System.out::println);
sqlSession.close();
}
4.5 添加数据
public interface BrandMapper {
void add(Brand brand);
}
<insert id="add">
insert into tb_brand (brand_name, company_name, ordered, description, status)
values (#{brandName},#{companyName},#{ordered},#{description},#{status});
</insert>
@Test
public void testAdd() throws IOException {
int status = 1;
String companyName = "波导手机";
String brandName = "波导";
String description = "手机中的战斗机";
int ordered = 100;
//封装对象
Brand brand = new Brand();
brand.setStatus(status);
brand.setCompanyName(companyName);
brand.setBrandName(brandName);
brand.setDescription(description);
brand.setOrdered(ordered);
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
SqlSession sqlSession = sqlSessionFactory.openSession(true); //设置自动提交事务
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
brandMapper.add(brand);
// sqlSession.commit(); // 注意提交事务
sqlSession.close();
}
获取主键
<insert id="add" useGeneratedKeys="true" keyProperty="id">
insert into tb_brand (brand_name, company_name, ordered, description, status)
values (#{brandName},#{companyName},#{ordered},#{description},#{status});
</insert>
SqlSession sqlSession = sqlSessionFactory.openSession(true);
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
brandMapper.add(brand);
Integer id = brand.getId();
System.out.println(id);
//sqlSession.commit();
sqlSession.close();
